Geochemistry and tectonic setting of basic dykes in the Boroujerd area (Sanandaj- Sirjan Zone)

• Main Authors: Zahra Tahmasbi, Hadis Ghasemifard, Ahmad Ahmadi khalaji, Leili Izadikian
• Format: Article
• Language: fas
• Published: University of Isfahan 2017-03-01
• Series: Petrology
• Online Access: http://ijp.ui.ac.ir/article_21586_51ea961a4f56263937926faf404edbb1.pdf

Basic dykes, trending NE-SW and cross cutting the middle Jurassic granodioritic rocksexposed in the Boroujerd area. They are dark green and fine to medium–grained rocksand are characterized by ophitic to subophitic texture. These rocks are dominated bymajor minerals including amphibole and plagioclase as well as minor biotite, apatite,sphene and prehnite. Amphibole is calcic, with magnesia-hornblende to actinolitehornblendecomposition. T = 600-700ºC and P = 3.5-5.2 kbar were calculated forcrystallization of these minerals. The composition of plagioclases ranges from albite tooligoclase. The basic dykes studied are undeformed and the youngest magmatic activityin the area.. The collision of Arabian and Central Iranian plates, gave rise to the pressurein the Central Iranian plate, which expanded the extension fractures in the direction ofthe plate movement. As a result, the dykes in discussion formed in direction of platemovement. Thus, development of basic dykes in the Northeast-Southwest direction withrespect to the convergence zone is justified. The basic dykes, on the discriminationtectonic diagrams, are classified as alkaline series and plotted on within plateenvironment field, which originated from partial melting of an enriched mantle source.